As a type of pad, there is known a seat pad used for a seat cushion of a vehicle seat (see JP-A-2010-125138). The seat pad is a member which forms an outer shape of a seat and elastically supports an occupant, and includes a surface layer pad corresponding to the first pad of the present disclosure and a back layer pad corresponding to the second pad of the present disclosure. The surface layer pad is a pad disposed on the seating side of the seat, and is formed, for example, of a polyurethane foam. A seating surface portion, which has a shape of occupying the entire seating surface of the seat, and a bulge portion, which protrudes from the seating surface portion to the back surface of the seat, are provided in the surface layer pad. The bulge portion is provided in a substantially central portion of the seating surface portion in a front and rear direction of the seat, and is disposed, for example, in such a position that the buttocks of the occupant can be supported. The back layer pad is a pad which is disposed on the back of the seat and supports the surface layer pad from below, and is formed of a material such as AS resin (styrene acrylonitrile resin) which is harder than the surface layer pad to be harder to bend. A hole which passes through the back layer pad in a thickness direction is provided in the back layer pad, and the bulge portion of the surface layer pad is disposed in the hole in a fitted state.
In the known art, the surface layer pad made of polyurethane foam can be molded by foaming a molding material in a mold cavity. At this time, the back layer pad made of AS resin is disposed in advance at a proper position inside the cavity so that the surface layer pad can be integrated with the back layer pad simultaneously with the molding. The bulge portion of the surface layer pad is molded to be in the state of being fitted in a hole of the back layer pad. At this time, when viewed from the back surface of the seat, the front and rear and right and left circumferential edges of the bulge portion are integrated with the inner surface side of the hole of the back layer pad. In this manner, the surface layer pad is supported by the back layer pad from below, and is covered with a seat cover. When the occupant is seated, the surface layer pad is pressed downward from the upper side to be appropriately bent and deformed. At this time, the bulge portion of the surface layer pad is strongly pressed by the buttocks of the occupant to be largely bent and deformed into the hole of the back layer pad.
In the known art, when viewed from the back surface of the seat, the front and rear and right and left circumferential edges of the bulge portion are integrated with the inner surface side of the hole of the back layer pad. That is, in the longitudinal and lateral directions orthogonal to a pressing direction, the bulge portion is integrated with the back layer pad, which is stiff so that it is harder to bend and deform, in an adjacent state. For this reason, in the known art, when the occupant is seated, and the bulge portion is largely bent and deformed, the portion which is integrated with the back layer pad cannot sufficiently follow the bending and deformation and prevents not to deform. The bulge portion is bent and deformed less than expected. Thus, for example, seating performance deteriorates, and an amount in which the occupant sinks into the seat cushion is decreased. Therefore, there is a concern that the hip point of the occupant is higher than a designed value.